This invention relates to dowel pins for dental models, and more particularly, to a dowel pin suitable for use in dental models which have removable dies.
In the making of dental crowns or bridge work, a starting point for the work of a dentist or dental technician is often a replica, accurate in shape and size, of the actual dentition of the patient. As was explained in U.S. Pat. No. 4,054,995, to Yoshida issued Oct. 25, 1977, and elsewhere, such replicas, referred to in dental terminology as "models", may be made by taking an impression of the patient's teeth and gums which provides a "negative" model of the patient's dentition. From the "negative", a "positive" can be cast in dental stone or plastic, and the positive forms the model from which a dental prosthesis may be prepared.
Typically, models are cast in a single piece, and then cut into segments encompassing perhaps one or two teeth, thereby to facilitate separation of the individual segments from the overall model for close study and individual use.
It is important that provision be made to precisely and positively relocate each segment with respect to the model when desired. For this purpose, various techniques and apparatus have been proposed. In one conventional and widely used system, tapered dowel pins are embedded in the model before molding of a base. After hardening of the base, the model can be removed from the base and cut into segments. The segments may thus be removed individually from the base, and returned to the base by insertion of the pins into the openings in the base cast.
In systems which have heretofore been proposed, numerous suggestions have been made for means to insure precise relocation of the dowel pins, and hence the die segments, with respect to the base. For example, in one system, tapered pins having a flat facet or V-shaped groove are used. In another, specially made pins which are rectangular or oval in cross-section are used. Such pins serve to "key" or orient the lingual, labial or buccal aspects, as the case may be, of the die segments to the desired orientation. Other pin systems, such as the one described in the above-mentioned U.S. Pat. No. 4,054,995, utilize sleeves or sockets embedded in the base, to receive and orient the ends of the pins. Other systems, such as the one illustrated in U.S. Pat. No. 3,937,773, to Huffman, issued Feb. 10, 1976, use a plurality of pins to establish the desired orientation of the die segment, while others, such as the one illustrated in U.S. Pat. No. 3,875,665, to Weissman, issued Apr. 8, 1975, employ pins which, in a unitary structure, provide in effect multiple pins.
It is an object of the present invention to provide a novel dowel pin for use in dental models which has all of the advantages of conventional single dowel pins, but which facilitates the removal from the model and the precise return of individual die segments.
It is a further object of this invention to provide a dowel pin which may be used in dental models without the need for cooperating parts such as sleeves, sockets or the like associated with the base, and still a further object to provide a dowel pin the use of which results in a durable and accurate model.
Other objects will appear hereinafter.